1. Field of the Invention
The present invention relates to a structure for attaching a scanning optical system, and more particularly to a structure for attaching a scanning optical system in which a scanning optical system in an optical scanning device used in a laser printer or the like is attached to an optical housing.
2. Description of the Related Art
As an attaching structure in which a scanning optical system in a conventional scanning optical system, which is employed widely in copying machines, laser printers, and the like, is attached to an optical housing, Japanese Patent Examined Publication No. Hei 3-56449 proposes attaching structures including the following: an attaching structure wherein flat portions are respectively formed in side portions of both surfaces of each of a biconcave lens, a meniscus lens, and a biconvex lens, and the flat portions are clamped by a holding member and a pressing member so as to attach the lenses to the optical housing, as well as an attaching structure wherein flat portions are respectively formed in side portions of one surface of each of a biconcave lens, a meniscus lens, and a biconvex lens, and each flat portion is held by a holding member while the other surface is pressed at one or a plurality of points by a pressing member or pressing members so as to attach the lenses to the optical housing. If a flat portion is formed on at least one surface of each lens, the flat portion can be brought into surface contact with the holding member, so that each lens can be positioned and held accurately. However, there are cases where it is difficult to form flat portions in such biconcave, meniscus lens, and biconvex lenses. Meanwhile, as shown in FIG. 6(a), with respect to a planoconcave lens or a planoconvex lens, there is no need to newly form a flat portion for being held by a holding member, and since a flat surface is already provided, if the flat surface is held by holding members 52 and 54, the lens can be positioned and held simply and accurately.
However, in the attaching structure for attaching to the optical housing the scanning lens constituted by the aforementioned planoconcave lens or planoconvex lens, since a flat surface S3 of a planoconvex lens, such as the one shown in FIG. 6(a), is held by the holding members 52 and 54, in the event that a convex surface S4 of the lens has changed from the convex surface S4 to a convex surface S4' due to a variation in the thickness of the lens owing to a production error, the direction of emergence of the laser beam from the lens changes from a direction B1 to a direction B2. Hence, the performance of the scanning optical system, particularly the linearity of the laser beam emergent from the scanning optical system, deteriorates, i.e., there occurs a large divergence with respect to the height of an ideal image. Consequently, there is a problem in that it is impossible to effect accurate scanning.
The above and other objects and features of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings.